'Alarming' Rise Seen in Drug-Resistant Tuberculosis

THURSDAY Aug. 30, 2012 -- There are alarmingly high levels of extensively drug-resistant tuberculosis in many areas of the world, a new study finds.

Researchers found high rates of resistance to at least one second-line drug (nearly 44 percent) among multidrug-resistant TB patients in eight countries in Africa, Asia, Europe and Latin America. They also found higher-than-expected overall levels of extensively drug-resistant TB.

Multidrug-resistant TB can withstand to at least two first-line drugs: soniazid and rifampicin. Extensively drug-resistant TB is resistant to isoniazid, rifampicin, a fluoroquinolone and a second-line injectable drug.

Fluoroquinolones are a class of antibiotics that include ciprofloxacin, levofloxacin and gatifloxacin.

For the study, samples collected from nearly 1,300 adults with multidrug-resistant TB in Estonia, Latvia, Peru, the Philippines, Russia, South Africa, South Korea and Thailand were tested for resistance to 11 first-line and second-line anti-TB drugs. Overall, in nearly 44 percent of patients, resistance to any second-line drug was detected. Rates ranged from 33 percent in Thailand to 62 percent in Latvia.

Overall, one-fifth of patients had resistance to at least one second-line injectable drug, ranging from 2 percent in the Philippines to 47 percent in Latvia. The overall rate of resistance to a fluoroquinolone was nearly 13 percent, ranging from 7 percent in the Philippines to 32 percent in South Korea.

Extensively drug-resistant TB was found in 6.7 percent of patients overall, with prevalence in South Korea (15 percent) and Russia (11 percent) more than twice the current World Health Organization estimate for the same time period (5.4 percent).

The researchers also found that the risk of extensively drug-resistant TB was more than four times higher in patients previously treated for TB, and that previous treatment with second-line drugs was the strongest risk factor for resistance.

The study was published online Aug. 29 in The Lancet.

"Drug-resistant TB is more difficult and costly to treat, and more often fatal. Internationally, it is particularly worrisome in areas with fewer resources and less access to effective therapies. As more individuals are diagnosed with, and treated for, drug-resistant TB, more resistance to second-line drugs is expected to emerge," lead author Tracy Dalton, of the U.S. Centers for Disease Control and Prevention, said in a journal news release.

"Most international recommendations for TB control have been developed for [multidrug-resistant] TB prevalence of up to around 5 percent. Yet now we face prevalence up to 10 times higher in some places, where almost half of the patients with infectious disease are transmitting [multidrug-resistant] strains," Sven Hoffner, from the Swedish Institute for Communicable Disease Control, wrote in an accompanying journal editorial.

"Updated information on [multidrug-resistant] TB and investigation of the trends are urgently needed...especially since the true scale of the burden of [multidrug-resistant] and [extensively drug-resistant tuberculosis] might be underestimated and seem to be rapidly increasing," he wrote.

More information

The U.S. Centers for Disease Control and Prevention has more about TB.